How do I stop hair particles going through the body and the head?
Collision with the emitter is not supported yet (2.77).

But there is a workaround for this problem. So you want to collide the hair with the emitter but there is no self collision? Well but collision with other objects works, right? Right! So you simply have to duplicate the entire emitter mesh and set it to a "fake self collider!

How it is done:


Step 1: Duplicate the emitter mesh (select the Mesh and hit shift+D. Right Click to place the mesh at the
same position as the original mesh).
Step 2: Go to the Object Menu and deselect all Ray Visibilities. This way the duplication will not get rendered. 
Step 2.5 (Optional): Now we want to eliminate the visibility of the duplication in the viewport. But simply restricting the view port visibility (by clicking the eye in the outliner) is not possible, because this way the collision may not be triggered. 
Change the display mode from "textured" to "bounds" in the Object Display Settings. This way your duplicated mesh will only get displayed as a box and will not generate any annoying clipping artifacts.

Step 3: Enable collision on the duplicated object. 

Step 4: Make sure everything is set up properly! In the modifier panel, the original emitter mesh should have the Armature at first position, followed by the Particles/Hair and followed by Subsurf.

Step 5: Also make sure the duplicated mesh has no Particle/Hair modifier. If it has one, you have to delete it in the particle panel!



Now your hair should collide correctly with the emitter!

If the hair still bugs into the body, try the following:
-in the hair dynamics setting, raise the "Quality" Amount (for me normally 5 Steps works just fine).
-in the collision settings of the collider, raise the "Outer face thickness" in the "Soft Body and Cloth" Settings.
-Raise the number of Subdivisions of the collider mesh (As i know, the collision does not get calculated by the faces of the collider but instead by the edges. If your mesh is to low poly the hair will slip through it)
-Raise the number of hair "segments" in the hair emitter settings.